It is now widely appreciated that research subjects often mistakenly believe they will achieve therapeutic benefits from participation in experimental trials. Understanding the nature and causes of this error is vital to improving the informed consent process. The OBJECTIVE of this proposal is to improve understanding of patients'reported expectations of benefit in early phase oncology trials. To accomplish this objective, we advance a new hypothesis to explain the purported error: Patients in early phase oncology trials exhibit unrealistic optimism (UO) in their assessment of the benefits and risks of participation in these trials. UO differs from previously studied phenomena on this issue, such as the therapeutic misconception. UO is a specific bias that leads an individual to believe that she is less likely to experience negative outcomes or more likely to experience positive outcomes than others who are similarly situated to her. Past research has amply demonstrated that UO influences judgments concerning susceptibility to a wide range of health risks and benefits. Our proposal is the first effort to gather data on the prevalence of UO in the context of clinical research. To accomplish our objective, we will pursue 2 specific aims: (1) To gather data on how patients enrolled in early phase oncology trials comparatively assess their susceptibility to general health risks/benefits and to specific research-related risks/benefits to others who are similarly situated. We will achieve this aim by using the Comparative Risk/Benefit Assessment Form. (2) To gather data on whether cognitive and motivational mechanisms that have been shown to evoke UO in other contexts are also present among patients in early phase oncology trials. We will achieve this aim by using the Health Problem Attributes Rating Form supplemented with qualitative interviews with patients. Findings from our proposal will lay the groundwork for further empirical and theoretical research on how social psychological factors, such as UO, impact informed consent in clinical research. PUBLIC HEALTH RELEVANCE: This proposal aims to improve understanding of why patient/subjects enrolled in early phase cancer trials have difficulty appreciating the risks and benefits associated with their own participation in these trials. It seeks to demonstrate how a phenomenon referred to as unrealistic optimism can explain persistently high expectations of therapeutic benefit in this population. Findings from this proposal will be used to improve the process of informed consent in clinical research.